1. Field of the Invention
The invention pertains to erection controls for precision gyroscopic stable platforms for providing precise attitude information relative to the vertical, and is also applicable to gyroscopic platforms for providing information about three mutually perpendicular reference axes with respect to a mobile craft; the invention provides a control arrangement for eliminating certain defects of the prior art whereby accelerometer errors cause the stable platform to be precessed in error.
2. Description of the Prior Art
The present invention is an improvement useful in stable gyroscopic platforms of the general type described in Charles B. Reed U.S. Pat. No. 3,648,525 for a "Gyroscopic Stable Reference Apparatus", issued Mar. 14, 1972 and assigned to the Sperry Rand Corporation. The present invention is also related generally to that disclosed in the J. R. Erspamer U.S. Pat. No. 3,931,747 for a "Gyroscopic Stable Reference Device", issued Jan. 13, 1976 and assigned to the Sperry Rand Corporation.
The invention of the Reed patent utilizes a relatively simple mechanical construction having five gyroscopically stabilized gimbals and only one servoed gimbal, thereby providing a stable platform relatively inexpensive, simple to manufacture, and reliable in operation. The gimballing arrangement of stable references like the Reed device provides an all-attitude capability, at the same time additionally yielding accurate attitude information with respect to the three orthogonal axes of the craft on which it is mounted. By stabilizing the directional gyroscope of the instrument in both pitch and roll, heading information is provided generally free from the gimbal errors of a conventionally mounted directional gyroscope.
While the original Reed device is a quite satisfactory instrument in many applications, it has certain defects of complex origin, some of which have been overcome, as described in the Erspamer application, and some of which evidence themselves more fully in precision airborne applications of the instrument. The defects of the prior art concepts will be developed in greater detail as the description of the invention progresses.